Variable vane turbos

[2nd.gunman]

i recently acquaired a new garret variable vane turbo off a mercedes diesel and am thinking of fitting it to 4.0lt i'm putting in the 68.

anyone have any info on variable vane turbos for performance use?

in the merc it pushes 2 bar at 4000rpm on a 5cyl 160hp diesel. huge amounts of torque.

 

[Anonymous]

the variable vane turbo is used on the International Diesel engines, namely the first one they had, the VT365 (Ford Powerstroke in 2003)

The main problem that we have had with these is that even when NEW, they rust inside and freeze up leading to the vanes sticking and low power.

They are best used when you need lots of boost at low RPM's while not sacrificing Turbine housing size for quick spool up. Im sure that it isnt Computer controlled like the Internationals, unless it is a new Mercedes, then it may be. In taht case, either a way to control the servo motor or ditch it and go manual control via manifold pressure.

Cummins/Holset also uses a variable turbo, but does not use vanes to control exhaust flow, instead, i believe it uses some type of eliptical collar that slides back and forth to control exhaust flow, dont qoute me on that. The Cummins/Holset turbo is a much more reliable design as they have not had many problems that i have heard of.

If you can make it work, they make good turbos with good slow RPM boost up to High RPM boost, as long as overspeeding sint an issue, hence controlling the speed somehow...

 

[2nd.gunman]

it's off a '04 model and is vacumn controlled, i work at a merc LCV dealership and as you say the only problem we've ever had with them is the diaphram sticking causing lack of power. i was wondering how it would react to manifold vacumn/boost from a petrol motor as opposed to from a vacumn pump on a diesel?

 

[Anonymous]

well a vacuum pump provides a continuous vacuum without change in pressure, basically (with slight variences in pressure output due to engine/pump speed) Where as a spark ignition engine only provides vacuum at closed to almost closed throttle (the more closed, the more vacuum)

This gives you a change in pressure according to RPM and engine load. a change in manifold pressure and load can be converted into a change in turbo pressure output as where a continuously runnign vacuum pump would have to have a controlled vacuum via a vacuum relay or some sort.

Is it Vacuum controlled with a controlled vacuum pump?..or boost controlled via the manifold pressure? For a 2004 i would think it is either boost controlled somehow or electronically controlled like all the other variable turbos that are being used on diesels now. I find that interesting...

 

[2nd.gunman]

i know it seems odd but there is a number of systems on these mercs that is vacumn controlled. even the headlight aim is on vacumn.

The vacumn systems are controlled by the CDI computer via switches off the main vacumn feed from pump. the turbo only sees vacumn signals, there is two connections, as far as i can tell one is for the variable vane function and the other is for an internal wastegate.

I'm not 100% sure of the connections as most of the turbos i see are traditional garret t04B's.

 

[Anonymous]

yeah...makes sense ...a controlled vacuum for a vane control and a wastegate control...ive never seen one..so im guessing at it...probably works well with varable vane and wastegate...a well controlled boost pressure.

Im not sure as to how you would get it to work for a spark ignition engine, there are ways, would be nice to have EFI blended with the CDI conrtoller you talk about...total control.

 

[63stl_comet]

The most popular turbo kit for Harley V Twins is a variable vane turbo setup. The whole idea behind the variable vane is to in effect change the size of the exhaust housing and eliminating for the most part any lag.

 

[xctasy]

Nissan in the Japan market ZR 200 released the first variable vane turbo. car put out 178 hp from a 2liter RB20ET engine. Turbo lag was vastly reduced, and the little in-line six had next to no low end torque to start with. It was the best application for a debut, but with the ZX 300 Turbo around, why would you buy a car with 50% less capacity?

Things haven't moved on much since then. On a diesel or any six, its a very good idea.

Take the F6 Typhoon and Tornado. These 9psi 362 hp, 400lb-ft beasts have noticable lag when cruising on the throttle, whereas the 6 psi 321 hp XR6 Turbo with the same turbo has no disceranable lag. The reason is the huge Garret GT40 turbo has a lot of inertia to overcome when you are trying to shove 9 psi through it at 1500 rpm.

A variable vane turbo could solve this. Mind you, the stock GT40 turbo is the best part of the whole package, and is big enough to produce well over 500 hp without being touched.

 

[2nd.gunman]

here's a pic it's a GT2256V

i'm a little worried that it might be a tad on the small side for a 4ltr but theres only one way to find out.[/img]

 

[Anonymous]

well the Turbine A/R is .54 from waht i can tell in the picture. That seems about right for a mild and quick 4.0, as fart as the compressor goes, it doesnt look too much bigger tahn the tubine, so im guessign a .60 A/R.

I may work, but you should finsd some specs on it to see what the compressor output is and then figure out what your 4.0L consumes in air.

Than take your specs to a compressor map and see how things line up...i dont know if you can find a compressor map for that or not, but possibly, it is a Garrtt GT turbo, there are lost of maps for those.

 

[2nd.gunman]

exhaust housing is A/R 0.64
intake housing is .53

i been struggling to find any maps for it. any ideas where i might find one?

 

[Anonymous]

Mercedes...if they have someone who is kind enough to offer it up and not treat you like you have no idea what your doing....you know how some engineers can be :roll:

here is one, there has to be, but as far as it being availiable to the public, who knows..you can do a search on the web...

This one might be the same turbine housing, but on a GT25, many housigns are interchageable thoguh, so it could be what you have, or damn close:

http://www.rbracing-rsr.com/turbo/TurboMaps/gt25rturbine.gif

This one is a Compressor map for a GT20, but like i said above, parts interchange alot between turbos. Mercedes could be using a larger turbine, for torque, but a smaller compressor to match the airflow.

http://www.rbracing-rsr.com/turbo/TurboMaps/GT20compress.jpg

But dont quote me and say it the exact one you have, but iahavea pretty good guess they just might be, maybe some more research can tell you that.

 

[Anonymous]

well the Turbine A/R is .54 from waht i can tell in the picture. That seems about right for a mild and quick 4.0, .

You are confused - - - - A/R is only the area/radius ratio - - - although it does affect spool-up time (per GIVEN application),


It has NOTHING to do with applications to engine SIZE (displacement).


Turbine trim (size of turbine exduced/inducer in mm) will dictate applicable turbo to engine displacement guidelines.


That compressor looks TINY. What is the inducer size? (mm?)

 

[StrangeRanger]

Linc.
Do you have anything definitive (formulae, graphs, nomograms, etc.) for sizing the turbine? The compressor side is easy once you find the map, but there seems to be way too much trial and error and/or black art involved in getting the right turbine.

 

[Anonymous]

Linc.
Do you have anything definitive (formulae, graphs, nomograms, etc.) for sizing the turbine?

There are just some relatively general guidelines, and it seems each turbo maker uses a differnet form of measurement.

Holset likes to use the area in square centimeters of their turbine exducer to size their turbines.

Garrett (formerly AiResearch) is a bit easier.

For T-3 turbos, there are three basic trim sizes, I am not into the T-3's but I know that the ones on the Chrysler 2.2 are pretty small and the Thunderbird and SVO were the next size larger.

On T4 size turbos (pretty much the most common) You have O, P and Q trim turbines. I use an O trim turbine on my TO4B, (with a .68 A/R housing)


As my car gets faster, I am starting to think about "uncorking" the exhaust side. That hurts spool time, but helps top HP. I do have a 1.00 A/R turbine housing (for O trim) that I am thinking of trying too see if top HP increases (will spool later though).

O trim turbines are really great for the size of engines we deal with. Their smaller diameter help them to spool faster than a P trim will. They are a little bigger than the larger T-3 turbines, so will allow a little better power up top. You will see the really hot 4 bangers and some turbo Buick guys using O trims. I think an O trim will flow enough hot air for up to around 500 HP.

If I start to get really serious about this engine, then I have enough spare parts to build up a TO4B with a P trim turbine. That probably won't happen, though. The really heavy hitting Buick guys are running P trims.

A P trim turbine is big enough for up to 800 HP or so, but that is really pushing it.

If you are into the T-3 size frame turbos, I would have to do more digging around for info. The Import car guys love the T-3/T4 hybrids that are pretty common lately. They use the fast spooling (small) hot side of a T-3 with the larger, higher flow TO4 compressors.

here is a good read, it deals with the T-3's but the info is good for all turbos:

http://www.turbominivan.com/tech/turbo201.htm

 

[Anonymous]

this is the only one i have ever seen, comes from Corky Bells book i believe:

Comparing Turbine exducer size requirement for compressor flow needs

 

[Anonymous]

That turbo is really too small for the 4-litre. It will max out HP wise before you even hit 300hp.

Here's the compressor map of the next size up, the GT2259.

Garrett recommends them for 160-280hp applications.

 

[2nd.gunman]

i am only looking for 5-7psi as the motor will be completely stock and i have no plans for other upgrades. i am only considering this because i got this turbo for free.

if the motor is going to overspeed the turbo or if the turbo is going to restrict the motor i won't go thru with it.